The present invention relates to a boring unit for pile foundations.
Excavations in the pile foundation sector are carried out via two different methods according to the kind of terrainxe2x80x94soft or hardxe2x80x94in which the excavation has to be carried out, and the two different methods therefore involve two different kinds of boring units.
Boring units of a well known type which are used for excavating soft terrain usually comprise a tracked vehicle, a mast which is supported by the vehicle, a rotary table which is slidingly mounted along the mast, and a telescopic rod, which is caused to rotate by the rotary table and which presents a boring tool at a lower end, the boring tool being suitable for breaking up the terrain and collecting the debris.
Boring units used for excavating soft terrain also comprise a head mounted on top of the mast, and present a single cable which is suitable for moving the telescopic rod and the tool between a lowered position for excavation, in which the tool is placed against the bottom of the hole, and a raised position for unloading, in which the tool is arranged outside the hole to permit the emptying of the debris.
In general, on the other hand, the boring units of a well known type which are used for excavating hard terrain comprise a fixed platform at the mouth of the hole, a determined number of hydraulic pistons which are supported by the platform, a rotary table which is incorporated into the platform, and a number of excavation rods, which are composed of hollow elements that may be coupled together by means of flanges, and which support at a lower end a boring tool which is suitable for breaking up the terrain.
The excavation rods used in the kind of boring units for hard terrain as described above are moved by the above-mentioned hydraulic pistons, the movement of which effects the depth of the excavation, and the boring units must also be equipped with centering devices and ballast for weighing down the tool. Furthermore, these kinds of units and their relative equipment are moved by a crane provided with a mast, and a head mounted on a top end of the mast itself, and presenting a hoist for effecting movement.
According to what has just been described above, it is quite obvious that carrying out some kinds of boring operations for pile foundations means that two kinds of different boring units must be used and that, furthermore, a crane must also be used, all of which means that it takes a long time to perform the excavation and that the costs are relatively high.
In The aim of the present invention is to produce a boring unit for pile foundations, which will permit the optimisation of the time needed for the excavation and which will also permit a considerable saving in terms of the machinery and equipment to be used.
According to the present invention, a boring unit for pile foundations will be realised comprising a platform facing the mouth of a hole, a mast which is supported by the platform, a rotary table slidingly mounted along the mast, and at least one excavation element which is connected to the table and which presents a boring tool at its lower end; the unit being characterised by the fact that it comprises a handling device of the excavation element and further auxiliary excavation elements which in turn comprise a head which is mounted at a top end of the mast, and which is provided with a hoist that may be connected to the excavation element, and which is also provided with a central cable which is suitable for moving the excavation element alternatively to the hoist between a lowered working position, in which the excavation element itself is arranged inside the hole, and a raised working position, in which the excavation element is arranged substantially outside the hole; the handling device also comprises a drive unit which is suitable for cooperating with the said hoist in order to rapidly move the auxiliary excavation elements.